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Grid tied inverter <1000watts ish

solarpv
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(Dave) #1

Hello, I’m looking for a small grid tied inverter that is controllable i.e. it’s power output is adjustable via serial of what ever. I don’t have a FiT tariff so therefore, would like to have a zero feed to the grid. I don’t want to create problems if the meter registers it’s been messed with if it gets back fed. Ideally I would like Node-red to control the inverter.

Dave.

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(Dave Howorth) #2

I don’t follow your logic here. You can install a system to turn down the output so it never exports, or you can just let it export although you don’t get paid. The first choice costs you money and hassle to install and maintain it, so why bother?

Meters nowadays don’t care about exports. They know it can happen and they just ignore it. If your meter is so old that it does have a problem, your electricity supplier will replace it free.

edit: A possible alternative would be to install a diverter to heat your water. That would reduce, but not eliminate exports, and would be useful to you.

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(Bill Thomson) #3

That depends on where one is located.

In some countries, utilities use meters that tally energy as an increase regardless of the
direction the energy flows through the meter. In that situation, you wind up paying for the
energy you’re producing vice getting paid for it.

While a diverter won’t completely eliminate energy export, I was able to “tune” one of Robin’s
diverters such that any export or import was so small it was negligible.

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(Brian Orpin) #4

Have you seen the section in ‘Learn’ about PV Diversion? Learn;→PV Diversion . If you do grid tie it you need a PV Diverter. For example Robin Emley’s Mk2 PV Diverter, see https://mk2pvrouter.co.uk but that is a kit.

You might consider not connecting it to the grid but simply connecting a hot water cylinder immersion to an off-grid inverter and switching the load off if the tank gets to maximum temperature. For a small array, the cost of the grid tie may be more than the payback.

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(Bill Thomson) #5

The only problem with that is a grid-tied inverter needs to be connected to the grid to function.
i.e. it won’t operate unless it is tied to the grid.

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(Brian Orpin) #6

Yes you need to get a non-grid tie one for off-grid purposes.

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(Dave) #7

I could have explained the idea better. Really it’s just messing with solar, control and power, just a few panels in the garden at first. I’m in the UK BTW where I’ve read somewhere if you back feed some meters they will show dot’s between the numbers to show an error?

(yes I do know what I’m doing and won’t electrocute anyone on the line if the power goes off etc I’m a qualified electrician albeit many years ago and familiar with control system, I used to design them!)

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(Bill Thomson) #8

That would necessittate separate circuits for devices powered by the inverter as connecting
a nongrid-tie inverter to the grid is a definite no-no.

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(Dave) #9

Thanks, I don’t think I’ve come across the mk2pvrouter before, no problem with electronics soldering etc I’ve been a radio ham for 36+ years :smile:

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(Brian Orpin) #10

You are correct but I thought that was obvious as the OP has said he is a qualified electrician and I did say just plug the immersion in and switch off when reaching temperature.

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(Bill Thomson) #11

You did fine, Dave. :grin:

Brian’s suggestion of a PV diverter is the way to go. I have one of Robin Emley’s diverters
and used it for the same purpose you want the variable output inverter for. i.e. to avoid
backfeeding the grid.

At the time, I had a meter that tallied energy use only in one direction. (up)

By using the diverter, I heated a 55 gallon drum of water to “burn” excess energy produced
by my PV system. That kept it from flowing back through my meter and hence me getting
charged for it.

Diverter operation is automatic. When energy is needed by other loads, the diverter reduces its
diversion of excess energy - or stops diverting it altogether. When those loads no longer
need energy, diverter operation resumes. All transparent to the user, and essentially instantly.

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(Bill Thomson) #12

True. But he also said he was looking for a grid-tied inverter. :wink:

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(Brian Orpin) #13

True, but the cost of the grid tying for a small array, when there can be no financial benefit (other than reduced use), opens up the possibility that a non-grid inverter might be the more cost effective option which the OP may not have considered.

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(Dave) #14

I have done, and really like Victron stuff and their open source side, but their prices are a bit high.

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(Dave) #15

From the other comments on immersion heaters, when had ours taken out along with the storage heaters when we had oil heating put in …

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(Bill Thomson) #16

I didn’t want to mess with my immersion heater, so I used a freestanding 55 Gallon drum of
water as a dump load. (at the time, my PV array totaled about 7.5kWp)

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(Bill Thomson) #17

Dave,

Have you seen this thread?

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(Dave) #18

Just remembered I did save two 750 watt elements from the storage heaters :thinking:

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(Bill Thomson) #19

Sounds like a plan! thumbsup

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(Bill Thomson) #20

highfive

I started in 1968.

73,
KR6K

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